Even relatively mild water limitation that causes reduced soil water potential (ψw) during drought can dramatically reduce plant growth and agricultural productivity. Detailed physiological analyses have shown that plant growth is actively down regulated during drought and not limited by carbon supply. The sensitivity of growth to low water potential has a wide range of genetic variabilities depending on the drought adaptation strategy employed by a specific plant genotype. Also, there are many specific metabolic pathways, for example proline metabolism, that are highly regulated by stress and contribute to stress tolerance. A strong reduction in growth in response to mild or moderate stress can help ensure survival by conserving water. However, it can be undesirable for agriculture as plant productivity is reduced more than it need be if growth were less sensitive to changes in water status.